1. Field of the Invention
The present invention relates to a remote control poppet valve in which a poppet in a poppet valve body is caused to move while following an input member.
2. Background of the Invention
Conventionally, as the remote control poppet valve of this kind as described above, there has been proposed a poppet valve as shown, for example, in FIG. 1.
This poppet valve will be briefly described. A poppet 12 for opening/closing a main flow path 11 is accommodated in a valve body 10. A pilot spool 13 provided integrally with a rod 14 is slidably inserted in the poppet 12 so as to constitute a pilot valve.
The rod 14 projects into a spring chamber 17 formed in a cover 15 fixed to the valve body 10 so as to be biased by a spring 18. The pilot spool 13 is pushed by a proportional solenoid 16 through the rod 14 so that the pilot spool 13 is positioned at a position where the force of the spring 18 is balanced with the output of the proportional solenoid 16.
The pilot valve of the poppet 12 and pilot spool 13 is changed over by the proportional solenoid 16 to take pressurized oil into and out of a back pressure chamber 19 so as to control the position of the poppet 12.
In such a conventional remote control poppet valve as described above, however, the poppet 12 is operated in such a manner that the poppet spool 13 is inserted into a center hole in the poppet 12 so as to constitute a pilot valve. The oil taken in from a flow inlet is taken into the back pressure chamber 19 through the pilot valve. On the other hand, the pilot oil is discharged from a flowing outlet communicated with the main flow path. Therefore, when the poppet is operated to open the main flow path, the pilot oil in the back pressure chamber flows into the main flow path from the flowing outlet, so that the pilot oil is added to that flowing into the main flow path between the inlet port and the outlet port.
As a result, the pilot oil flows as an instantaneously formed flow while it is a small quantity. Therefore, there has been such a problem that a cylinder positioned downstream is instantaneously moved.
Further, even when the poppet is controlled so as to fully close the main flow path, the fully closed state is not perfectly realized because there exists a leakage from the pilot spool 13 to the flow outlet. Furthermore, there has been such a problem that an emergency operation cannot be performed when the pilot spool 13 becomes inoperative because the poppet 12 is controlled only by the pilot spool 13.
Another type of a conventional poppet valve will be briefly described with reference to FIG. 2. A poppet 102 is accommodated in a valve body 101 and is urged in the direction to close the valve by a spring 103. In the poppet 102, a passage having a orifice 104 is formed for causing an inlet port 105 to communicate with a back pressure chamber 106. A passage 109 having a conical opening portion 108 is formed for causing the back pressure chamber 106 to communicate with an outlet port 107.
The poppet 102 is caused to follow an input rod 110 with an orifice 111 formed between the poppet 102 and a front end portion of the input rod 110. That is, when the input rod 110 is pushed right in the drawing, The orifice 111 is closed to thereby increase a pressure in the back pressure chamber 106 so that the right edge of the poppet 102 is caused to come into close contact with a seat portion 112 to thereby close a flow path between the inlet and outlet port 105 and 107 as shown in the drawing.
When the input rod 110 is caused to move left in the drawing, on the contrary, the poppet 102 moves while following the input rod 110. As a result, the poppet 102 is separated from the seat portion 112 to thereby open the flow path.
In such a second conventional remote control poppet valve as described above, however, a simple rodlike operation rod 110 projects outwards from the back pressure chamber 106 so that a pressure at the outlet port 107 acts on a sectional area of the operation rod 110. Accordingly, a large operation force was required to cause the poppet to move while following the input rod which was driven at an exceedingly high speed. Consequently, the conventional remote control poppet valve is unsuitable for high-speed driving.
Furthermore, similarly to the first conventional poppet valve, even if the operation for opening the flow path between the inlet and outlet ports 105 and 107 is performed at a high speed, pilot oil instantaneously flows from the back pressure chamber 106 into the outlet port 107 so that the flow is added to the original one. Therefore, there has been such a problem that a cylinder or the like located downstream the outlet port 107 is caused to move instantaneously.
Further, even when the poppet is controlled so as to fully close the flow path, there has been such a problem that if a leak occurs at the orifice 111, this leakage appears at the outlet port 107 as it is. Moreover, the poppet is controlled only by the operation rod 110. Accordingly, there has been such a problem that an emergency operation cannot be performed in the case where it becomes impossible to operate the operation rod 110 for some reason.